Friday, February 21, 2014

New paper finds North Pacific was warmer in 1930's than at end of 20th century

Another day, another non-hockey-stickA paper published today in Climate of the Past reconstructs climate of the North Pacific over the 261 year period from 1736-1997 and finds another non-hockey-stick of temperature and precipitation, with higher values in the 1930's-1940's than at the end of the record in 1997. The paper adds to more than 1,200 peer-reviewed, published non-hockey-sticks demonstrating that there is nothing unusual, unnatural, or unprecedented about late 20th century temperatures or precipitation.

dD hydrogen isotope proxy for temperature & precipitation shows temperature and precipitation were higher in the 1930's-1940's than at the end of the record in 1997. Note horizontal axis has end of record on left side of graph.

Abstract. An ice core was retrieved in June 1998 from the Gorshkov crater glacier at the top of the Ushkovsky volcano, in central Kamchatka. This ice core is one of only two recovered from Kamchatka so far, thus filling a gap in the regional instrumental climate network. Hydrogen isotope (δD) analyses and past accumulation reconstructions were conducted for the top 140.7 m of the core, spanning 1736–1997. Two accumulation reconstruction methods were developed and applied with the Salamatin and the Elmer/Ice firn-ice dynamics models, revealing a slightly increasing or nearly stable trend, respectively. Wavelet analysis shows that the ice core records have significant decadal and multi-decadal variabilities at different times. Around 1880 the multi-decadal variability of δD became lost and its average value increased by 6‰. The multi-decadal variability of reconstructed accumulation rates changed at around 1850. Reconstructed accumulation variations agree with ages of moraines in Kamchatka. Ice core signals were significantly correlated with North Pacific sea surface temperature (SST) and surface temperature (2 m temperature). δD correlates with the North Pacific Gyre Oscillation (NPGO) index after the climate regime shift in 1976/1977, but not before that. Therefore, our findings imply that the ice core record contains various information on the local, regional and large-scale climate variability in the North Pacific region. Understanding all detailed mechanisms behind the time-dependent connections between these climate patterns is challenging and requires further efforts towards multi-proxy analysis and climate modelling.